Here is the full list of all 16 Keen Dreams achievements.
Get the maximum possible score in Spud City
Complete the game on "Normal" difficulty.
Complete an entire game in CGA mode.
Complete the game on "Easy" difficulty.
Collect all 24 Boobus Bombs
Get the maximum possible score in the Melon Mines
Complete the game on "Hard" difficulty.
Complete Castle Tuberia with the highest possible score
Complete Grape Grove with the highest possible score.
Get the maximum possible score at Bridge Bottoms
Complete Squash Swamp with the highest possible score.
Get the maximum possible score at Parsnip Pass
Compete Brussel Sprouts Bay with the highest possible score.
Complete Apple Acres with the highest possible score.
Get the maximum possible score on Horseradish Hill